Driving apparatus, image forming apparatus, method of driving control and program

ABSTRACT

There is provided a driving apparatus comprising: a driving unit configured to rotate a driving shaft; a speed setting unit for setting a rotational speed of the driving shaft; a driving shaft joint connected with the driving shaft to rotate with the driving shaft for transmitting driving-force to a driven apparatus, the driving shaft joint being fitted into a driven shaft joint connected with the driven apparatus that is made detachable; a rotational position detection unit configured to detect a predetermined rotational position of the driving shaft joint; and a driving control unit configured to control the driving unit; wherein upon the driven apparatus being detached, the driving control unit controls the driving unit to stop the rotating driving shaft based on a detection result of the rotational position detection unit after the speed setting unit sets the rotational speed of the driving shaft to be a first rotational speed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present technology relates to a driving apparatus, an image formingapparatus, a method of driving control and a program.

2. Description of the Related Art

For example, in an electrophotographic image forming apparatus, unitssuch as a developing device or a fixing device are provided detachablyfrom a main body so that the units can be replaced upon a failureoccurring. The respective units are coupled with the main body through apair of couplings that are disposed at respective driving shafts andfitted into each other, and a developing roller or a fixing roller,etc., included in the respective units are rotated upon receivingdriving-force from the main body through the couplings.

A structure is disclosed in which a deformable coupling part coveredwith an elastic member is provided so that vibration or degradation ofdurability due to collisions of the couplings caused byattaching/detaching the units can be prevented (for example, PatentDocument 1).

However, according to a structure disclosed in Patent Document 1,manufacturing cost for parts and assembly may be increased since thedeformable coupling part is required.

RELATED ART DOCUMENT Patent Document

[Patent Document 1]: Japanese Laid-open Patent Publication No.2011-99537

SUMMARY OF THE INVENTION

An object of disclosure of the present technology is to provide adriving apparatus which can maintain durability of a coupling part forcoupling the driving apparatus with an apparatus driven by the drivingapparatus.

The following configuration is adopted to achieve the aforementionedobject.

In one aspect of the embodiment, there is provided a driving apparatuscomprising: a driving unit configured to rotate a driving shaft; a speedsetting unit configured to set a rotational speed at which the drivingunit rotates the driving shaft; a driving shaft joint connected with thedriving shaft to rotate with the driving shaft for transmittingdriving-force to a driven apparatus, the driving shaft joint beingfitted into a driven shaft joint connected with the driven apparatusthat is made detachable; a rotational position detection unit configuredto detect a predetermined rotational position of the driving shaftjoint; and a driving control unit configured to control the drivingunit; wherein upon the driven apparatus being detached, the drivingcontrol unit controls the driving unit to stop the rotating drivingshaft based on a detection result of the rotational position detectionunit after the speed setting unit sets the rotational speed of thedriving shaft to be a first rotational speed, the first rotational speedbeing less than a normal rotational speed of the driving shaft set innormal operation of the driven apparatus.

Other objects, features and advantages of the present invention willbecome more apparent from the following detailed description when readin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for illustrating a configuration of an image formingapparatus of the present embodiment.

FIG. 2 is a diagram for illustrating an example configuration of thedriving apparatus of the present embodiment.

FIG. 3A is a front view of the drive side coupling.

FIG. 3B is a side view of the drive side coupling.

FIG. 4A is a front view of the developing side coupling.

FIG. 4B is a sectional view in A-A shown in FIG. 4A.

FIG. 5 is a diagram for illustrating stop position of the coupling.

FIG. 6 is a diagram for illustrating an example relationship between thevariance of stop position of the drive side coupling and the rotationalspeed of the motor.

FIG. 7 is a flowchart for illustrating an example of motor controlprocess of the first embodiment.

FIG. 8 is a diagram for illustrating an example motor control in thefirst embodiment.

FIG. 9 is a diagram for illustrating an example relationship between thevariance of stop position of the drive side coupling and the rotationalspeed of the motor in the second embodiment.

FIG. 10 is a flowchart for illustrating an example motor control processof the second embodiment.

FIG. 11 is a diagram for illustrating the motor control in the secondembodiment.

FIG. 12 is a flowchart for illustrating an example motor control processof the third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Herein below, embodiments will be described with reference to theaccompanying drawings. Additionally, in respective embodiments,identical reference numerals will be applied to an elements or the likethat have substantially similar functions and configurations to those inanother embodiment, and descriptions thereof may be omitted.

<Image Forming Apparatus>

FIG. 1 is a diagram for illustrating a configuration of an image formingapparatus 1 of the present embodiment.

The image forming apparatus 1 includes image forming units 10Y, 10M,100, 10K and 10S, toner supply units 20Y, 20M, 20C, 20K and 20S, afixing device 50 and an operational unit 60. The image forming apparatus1 forms an image on a paper “P” conveyed from paper feeding units 30 and31.

Additionally, respective reference characters “Y”, “M”, “C”, “K” and “S”indicate toner colors of yellow, magenta, cyan and black, andhereinafter descriptions of these colors may be omitted. Also, “specialcolor” means a tonner color used for color reproduction for forming animage which cannot be formed by conventional yellow, magenta, cyan andblack, in a case such as forming an image by using white toner on apaper whose color is other than white, or glossing an image by usingtransparent toner.

The image forming unit 10 includes a photoconductor drum 2, a chargingdevice 3, a developing device 4, a primary transfer roller 5, a cleaningdevice 6 and a discharging device 7. The image forming unit 10 formstoner images in respective colors on a surface of an intermediatetransfer belt 8.

The photoconductor drum 2 is rotated in an arrow direction shown in FIG.1, and an electrostatic latent image is formed by a writing device (notshown) based on image data after charging a surface of thephotoconductor drum 2 by the charging device 3. The electrostatic latentimage formed on the surface of the photoconductor drum 2 is transformedinto a toner image by having the respective colors of toner adherethereto by the developing device 4, thereby being transferred to theintermediate transfer belt 8 in between the photoconductor drum 2 andthe primary transfer roller 5.

The photoconductor drum 2 whose toner image is transferred to theintermediate transfer belt 8 continues to be rotated to be removed thetoner adhered thereto by the cleaning device 6, then it's surface isdischarged by the discharging device 7 to prepare for next imageforming.

Toner images formed by the respective colors of image forming units 10are transferred to the intermediate transfer belt 8 in piles. A tonerimage composed of the toner images formed in piles on the surface of theintermediate transfer belt 8 are conveyed to a secondary transfer roller9 with the intermediate transfer belt 8 rotationally driven by therollers, and the toner image is transferred to the paper P conveyed fromthe paper feeding units 30 and 31 by a conveyance roller 40 and thelike.

Upon the toner image being transferred on the surface of the paper P,the paper P is conveyed to the fixing device 50 to be heated and pressedso that the toner image is fixed on the paper P, then the paper P isejected out of the apparatus.

For example, the operational unit 60 of the image forming apparatus 1includes a display device such as a liquid crystal panel, keypad, etc.,and accepts respective operations, setting changes, etc., from a user ofthe image forming apparatus 1.

In the image forming apparatus 1, respective units in the image formingunit 10 such as a developing device 4, the intermediate transfer belt 8,the secondary transfer roller 9, the fixing device 50, etc., are formedto be detachable from the main body so that they can be replaced, or thelike if needed.

Detachable units such as the developing device 4 are provided in amanner such that a coupling disposed at the driving shaft of thedetachable unit is fitted into a coupling disposed in the main body,thereby transmitting driving-force from a motor disposed in the mainbody to the detachable unit through the couplings. For example, thedriving shaft of the developing device 4 is rotated by the driving-forcetransmitted from the motor disposed in the main body through a coupling,thereby rotating a developing roller, stirring screw, and the like.

<Driving Apparatus>

In the following, a driving apparatus 100 disposed in the image formingapparatus 1 will be described. In the following, the driving apparatus100 drives the developing device 4 provided as the detachable unit.

FIG. 2 is a diagram for illustrating an example configuration of thedriving apparatus 100 of the present embodiment.

As shown in FIG. 2, the driving apparatus 100 includes a control device110, a motor driver 120, a motor 130, a driving shaft 140, a rotationalposition detection sensor 150 and a drive side coupling 160.

The control device 110 includes a motor speed setting unit 111, a motorcontrol unit 112, a rotational position acquiring unit 113 and a tonerresidual amount acquiring unit 114. For example, the control device 110includes a CPU, a ROM, a RAM, etc., and functions of the respectiveunits are achieved by executing programs stored in the ROM by CPU incooperation with the RAM.

The motor speed setting unit 111 sets a rotational speed of the motor130 for rotating the developing roller 410, etc., in the developingdevice 4 in accordance with image forming condition, etc., set for theimage forming apparatus 1.

The motor control unit 112 is an example of driving control unit, and ittransmits a control signal to motor driver 120 so as to rotate the motor130 at a rotational speed set by the motor speed setting unit 111. Forexample, the motor control unit 112 transmits a clock signal, a PWMsignal, etc., to the motor driver 120 as the control signal. By changinga frequency of the clock signal, the rotational speed of the motor 130can be controlled. By changing an active level duty of the PWM signal,the rotational speed of the motor 130 can be controlled.

For example, the motor control unit 112 can start or stop rotating themotor 130 by transmitting an enable signal to the motor driver 120. Forexample, the motor control unit 112 transmits the enable signal at a lowlevel to start rotating the motor 130, while it transmits the enablesignal at a high level to stop rotating the motor 130.

Further, in a case where the motor 130 has a brake function, the motorcontrol unit 112 can actuate the brake function of the motor 130 bytransmitting a brake signal to the motor driver 120. By transmitting thebrake signal to actuate the brake function, the motor control unit 112can stop the motor 130 quicker than by transmitting the enable signal tohave the motor 130 freewheel, and thereby stopping the motor 130.

The rotational position acquiring unit 113 acquires a detection resultof the rotational position detection sensor 150 for detecting a certainrotational position of the driving shaft 140 rotated in connection withthe motor 130.

The toner residual amount acquiring unit 114 acquires residual amount ofthe toner remaining in a sub-hopper 22 from a residual amount detectionsensor 23 disposed in a toner supply unit 20.

The motor driver 120 rotates the motor 130 based on the control signaltransmitted from the motor control unit 112. Also, for example, themotor driver 120 transmits the lock signal at the low level to the motorcontrol unit 112 in a case where the rotational speed of the motor 130does not reach the set rotational speed, while it transmits the locksignal at the high level to the motor control unit 112 in a case wherethe rotational speed of the motor 130 reaches the set rotational speed.

The motor 130 is an example of driving unit, and it rotates undercontrol of the motor control unit 112 through the motor driver 120. Thedriving shaft 140 is connected to the motor 130 to rotate in accordancewith the motor's rotation.

For example, the motor 130 is a DC motor, and preferably has the brakefunction. When having the brake function, the rotating motor 130 can bestopped more quickly by actuating the brake function controlled by themotor control unit 112.

The rotational position detection sensor 150 is an example of rotationalposition detection unit, and includes a rotational member 151, atransmission photo sensor 152. For example, the rotational member 151 isa rod-like member fixed in a manner such that the rotational member 151is extended from the center of rotational axis of the driving shaft 140toward outside in a diameter direction. The rotational member 151 isrotated with the driving shaft 140.

The transmission photo sensor 152 includes a light emitting part and alight receiving part, and detects the rotational member 151 when therotational member 151 rotated with the driving shaft 140 interrupts anoptical path between the light emitting part and the light receivingpart, thereby transmitting the detection result to the rotationalposition acquiring unit 113 of the control device 110.

The rotational position detection sensor 150 is provided to detect therotational member 151 by the transmission photo sensor 152 when thedrive side coupling 160 connected with the driving shaft 140 is at acertain rotational position. Additionally, the rotational positiondetection unit may have a configuration different from the rotationalposition detection sensor 150 of the present embodiment as long as itcan detect that the drive side coupling 160 is at the certain rotationalposition.

The drive side coupling 160 is an example of driving shaft joint, and itis provided to be fixed at an end of the driving shaft 140, therebyrotating with driving shaft 140 in accordance with the motor 130. Also,the drive side coupling 160 is fitted into a developing side coupling430 included in the developing device 4, and thereby transmits thedriving-force from the motor 130 to the developing device 4.

The developing device 4 is an example of driven apparatus, in which adeveloping roller 410, a developer conveyance screw (not shown), etc.,are connected with a driven shaft 420, where the developing sidecoupling 430 is disposed at the driven shaft 420 as a driven shaftjoint. The developing roller 410 rotates at a certain rotational speedreceiving the driving-force from the motor 130 of the driving apparatus100.

The developing roller 410 is an example of developing unit. For example,the developing roller 410 to which developing bias is applied rotatesholding developer including toner and carrier to form the toner image byhaving the toner adhere to the electrostatic latent image formed on thesurface of the photoconductor drum 2. Also, a toner outlet 411 forejecting redundant toner is provided in the developing device 4.

The toner supply unit 20 is an example of toner supply unit, andincludes a toner bottle 21, a sub-hopper 22 and the residual amountdetection sensor 23.

The toner bottle 21 stores toner whose color corresponds to thedeveloping device 4, and for example, it rotates to eject the toner tothe sub-hopper 22. The sub-hopper 22 temporarily retains the tonerejected from the toner bottle 21 and supplies the retained toner to thedeveloping device 4. For example, the toner is supplied from thesub-hopper 22 to the developing device 4 through a diaphragm pump (notshown) as required.

The residual amount detection sensor 23 is an example of residual amountdetection unit for detecting residual amount of the toner in thesub-hopper 22 to report the detection result to the toner residualamount acquiring unit 114 of the control device 110. For example, theresidual amount detection sensor 23 is configured by a piezoelectricsensor, optical sensor, etc., disposed on an inner surface of thesub-hopper 22. However, the residual amount detection sensor 23 may beconfigured by other elements as long as it can detect the residualamount of the toner.

<Coupling>

In the following, the drive side coupling 160 and the developing sidecoupling 430 for connecting the driving apparatus 100 and the developingdevice 4 will be described.

FIG. 3A and FIG. 3B are diagrams for illustrating an example of driveside coupling 160. FIG. 3A is a front view of the drive side coupling160. FIG. 3B is a side view of the drive side coupling 160.

As shown in FIG. 3, the drive side coupling 160 includes a columnarportion 161 and projecting portions 170 projecting from outer surface ofthe columnar portion 161. The drive side coupling 160 is fixed at an endof the driving shaft 140 to rotate with the driving shaft 140 driven bythe motor 130.

The columnar portion 161 is fixed at an end of the driving shaft 140 ina manner such that a center axis direction thereof is in parallel withthe driving shaft 140. The projection portions 170 are provided at threepositions on the outer surface of the columnar portion 161 extending inparallel with the center axis direction of the columnar portion 161,where the projection portions 170 are spaced apart from each other incircumferential direction by equal distance. The respective projectingportions 170 include a pointed end 171 extending in a direction oppositeto the driving shaft 140, incline surfaces 172 and drive transmissionsurfaces 173.

FIG. 4A and FIG. 4B are diagrams for illustrating an example ofdeveloping side coupling 430. FIG. 4A is a front view of the developingside coupling 430. FIG. 4B is a sectional view in A-A shown in FIG. 4A.

As shown in FIG. 4, the developing side coupling 430 includes acylindrical portion 431, projecting portions 440 projecting from innersurface of the cylindrical portion 431. The developing side coupling 430is fixed at an end of the driven shaft 420 of the developing device 4.

The cylindrical portion 431 has a hollow cylindrical shape shielded itsend at the driven shaft 420 side. The cylindrical portion 431 is fixedat an end of the driven shaft 420 in a manner such that the center axisdirection thereof is in parallel with the driven shaft 420. Theprojecting portions 440 are provided at three positions on the innersurface of the cylindrical portion 431 extending in parallel with thecenter axis direction of the cylindrical portion 431, where theprojection portions 440 are spaced apart from each other incircumferential direction by equal distance. The respective projectingportions 440 include a pointed end 441 extending in a direction oppositeto the driven shaft 420, incline surfaces 442 and driven transmissionsurfaces 443.

The drive side coupling 160 and the developing side coupling 430 arecoupled with each other by inserting the columnar portion 161 into thecylindrical portion 431 where the respective projecting portions 170 ofthe drive side coupling 160 are inserted between the projecting portions440 of the developing side coupling 430.

Upon the motor 130 being driven where the drive side coupling 160 andthe developing side coupling 430 are coupled with each other, the driveside coupling 160 is rotated with the driving shaft 140. Upon the driveside coupling 160 rotating, the driving-force of the motor 130 istransmitted since the drive transmission surface 173 of the drive sidecoupling 160 is in contact with the driven transmission surface 443 ofthe developing side coupling 430, which causes both surfaces to beengaged with, thereby rotating the developing side coupling 430 and thedriven shaft 420.

Here, for example, in a case where the developing device 4 is replacedwith new one in the image forming apparatus 1, depending on therotational position of the drive side coupling 160 and the developingside coupling 430, the projecting potion 170 may be inserted in a mannersuch that it collide with the projecting portion 440.

For example, in a case where the pointed end 171 of the drive sidecoupling 160 hits against the pointed end 441 or the incline surface 442of the developing coupling 430 and the pointed end 441 of the developingside coupling 430 hits against the pointed end 171 or the inclinesurface 172 of the drive side coupling 160, the hit portions may bedamaged.

Therefore, in the driving apparatus 100 of the present embodiment, themotor 130 is controlled so that the drive side coupling 160 is stoppedat a certain rotational position at least when the developing device 4is detached. If the drive side coupling 160 is stopped at the certainrotational position, the aforementioned collision can be avoided so asto prevent the damage of the respective portions in replacing thedeveloping device 4 by adjusting the rotational position of thedeveloping side coupling 430 in a newly attached developing device 4.

As shown in FIG. 5, the developing side coupling 430 of the presentembodiment, the projecting portions 440 are formed so that they arespaced apart from each other in circumferential direction by 60°.Therefore, for example, by stopping the drive side coupling 160 so thatthe pointed end 171 is stopped within a range of angles±30° from areference line (“0°” shown in FIG. 5), the pointed end 171 can beinserted without hitting against the projection portion 440 of thedeveloping side coupling 430, where “0” shows the center axis in FIG. 5.

However, preferably, the drive side coupling 160 is controlled so thatthe pointed end 171 is stopped within a range of angles±15° from areference line (“0°” shown in FIG. 5), taking into account individualdifference of the rotational positions of the developing side couplings430 of the developing device 4.

In the present embodiment, the motor control unit 112 transmits theenable signal at the high level to the motor driver 120, thereby havingthe motor 130 stopped. In response to the enable signal at the highlevel, the motor driver 120 has the motor 130 freewheel, and therebystopping the motor 130.

When the motor 130 freewheels to stop, the rotational position (stopposition) at which the motor 130 is stopped varies. The variance of thestop position of the motor 130 causes variance of the stop position ofthe drive side coupling 160 rotating with the motor 130, and thevariances of the stop positions depends on the rotational speed of themotor 130.

FIG. 6 is a diagram for illustrating an example relationship between thevariance of stop position of the drive side coupling 160 and therotational speed of the motor 130.

As shown in FIG. 6, the variance of the stop position becomes greater asthe rotational speed of the motor 130 becomes greater and it becomessmaller as the rotational speed of the motor 130 becomes smaller.Therefore, for example, the motor 130 needs to be controlled to drive atthe rotational speed equal to or less than V1 in order to have the driveside coupling 160 stop at a rotational position within a range ofangle±15° (30° in total) from a target rotational position.

Here, for example, the rotational speed V1 is less than a rotationalspeed of the motor 130 when the motor 130 is normally driven (rotationalspeed of the motor 130 in normal drive), e.g., when forming an image inthe image forming apparatus 1. Additionally, the normal drive means acase where the developing device 4 is driven for forming an image by theimage forming apparatus 1, etc., that is, a case where the drivenapparatus connected with the motor 130 operates so as to function.

Thus, the motor 130 and the drive side coupling 160 can be stopped at arotational position within a predetermined rage from the targetrotational position by controlling the rotational speed of the motor 130to be equal to or less than the rotational speed V1 set in the normaldrive.

Additionally, in the examples described above, the shapes orconfigurations of the drive side coupling 160 and the developing sidecoupling 430 are not limiting examples. They may be different from thoseshown in the examples described above as long as the driving-force ofthe motor 130 is transmitted to the driven shaft 420.

Also, the stop position of the drive side coupling 160 is set accordingto a shape for coupling with the developing side coupling 430. Further,the rotational speed of the motor 130 is set based on variance of thestop position fluctuated depending on shapes of the drive side coupling160 and the developing side coupling 430, or the like.

<Motor Control Process>

In the following, first to third embodiments of a process forcontrolling motor 130 when detaching the developing device 4 will bedescribed.

First Embodiment

FIG. 7 is a flowchart for illustrating an example of motor controlprocess of the first embodiment.

For example, in a case where the developing device 4 is detached fromthe image forming apparatus 1 to be replaced with new one, as shown inFIG. 7, in step S101, the motor speed setting unit 111 sets therotational speed of the motor 130. For example, the rotational speed ofthe motor 130 is set to be equal to or less than the rotational speed V1which is less than the rotational speed of the normal drive for formingan image by the image forming apparatus 1, etc., and where the varianceof the stop position of the drive side coupling 160 can be suppressed tobe within a predetermined range of the rotational position.

In step S102, the motor control unit 112 transmits the enable signal atthe low level to the motor driver 120 to have the motor 130 rotate atthe rotational speed set by the motor speed setting unit 111.

In step S103, the motor control unit 112 determines whether therotational speed of the motor 130 reaches the set rotational speed basedon the lock signal transmitted from the motor driver 120.

In a case where the rotational speed of the motor 130 is determined toreach the set rotational speed, the process is proceeded to step S104,and the rotational position acquiring unit 113 acquires the detectionresult of the rotational position detection sensor 150 and determineswhether the rotational position of the driving shaft 140 and the driveside coupling 160 reaches a predetermined rotational position.

The rotational position detection sensor 150 is configured so as todetect a rotational position of the drive side coupling 160, where thestop position of the drive side coupling 160 comes within a target rangewhen the motor 130 stops after freewheeling. That is, the transmissionphoto sensor 152 detects the rotational member 151 upon the drive sidecoupling 160 reaching a predetermined rotational position.

Upon the rotational position detection sensor 150 detecting that thedrive side coupling 160 is at the predetermined rotational position, themotor control unit 112 transmits the enable signal at the high level tothe motor driver 120 to stop the motor 130 in step S105.

FIG. 8 is a diagram for illustrating an example motor control in thefirst embodiment.

FIG. 8 is a timing diagram for illustrating waveforms of signals forperforming the process shown in FIG. 7 in order to detach the developingdevice 4 after the motor 130 has been driven in a normal state then,stopped. As shown in FIG. 8, for example, the motor control unit 112outputs the clock signal at a frequency for having the motor 130 rotateat the rotational speed set by the motor speed setting unit 111 to themotor driver 120. In detaching the developing device 4, a frequency ofthe clock signal becomes lower in comparison to that in normal drive.Also, in a case where the developing device 4 is detached, the motorcontrol unit 112 transmits the enable signal at the low level to themotor driver 120, thereby having the motor 130 start to rotate.

Upon the rotational speed of the motor 130 reaching the set rotationalspeed, the lock signal at the high level is transmitted from the motordriver 120 to the motor control unit 112. When detaching the developingdevice 4, upon the rotational position acquiring unit 113 receiving adetection signal from the rotational position detection sensor 150during the motor 130 rotating at the set rotational speed, the motorcontrol unit 112 transmits the enable signal at the high level to themotor driver 120 to stop driving the motor 130. Here, the lock signal atthe low level is transmitted from the motor driver 120 to the motorcontrol unit 112 upon the rotational speed of the motor 130 becoming theset rotational speed.

Additionally, in the normal drive, the motor control unit 112 does nothave the motor 130 stop even if the rotational position acquiring unit113 receives the detection signal from the rotational position detectionsensor 150. Also, the rotational position acquiring unit 113 may startto receive the rotational position detection signal from the rotationalposition detection sensor 150 after certain period (e.g., severalseconds) passes from a timing at which the lock signal at the high levelis transmitted from the motor driver 120 to the motor control unit 112in a case where the developing device 4 is detached.

Additionally, although in the example shown in FIG. 8, the motor controlprocess starts in a state where the motor 130 is stopped, the motorcontrol process of the first embodiment may start in response to anoperation mode being set to be a replacement mode of the developingdevice 4 while the motor 130 is driven. In this case, the motor controlunit 112 has the frequency of the clock signal be lower upon aninstruction indicating that the developing device 4 will be detachedbeing given to the motor control unit 112. When the frequency of theclock signal becomes lower, the lock signal at the low level is outputfrom the motor driver 120 since the motor 130 does not rotate at therotational speed set for the normal drive. When the rotational speed ofthe motor 130 becomes the rotational speed set for detaching thedeveloping device, the lock signal at the high level is output from themotor driver 120. When the rotational position acquiring unit 113receives the detection signal from the rotational position detectionsensor 150 after the lock signal at the high level has been output fromthe motor driver 120, the motor control unit 112 transmits the enablesignal at the high level so as to stop the motor 130.

For example, in a case where the developing device 4 is detached to bereplaced with new one in the image forming apparatus 1, the drive sidecoupling 160 is stopped at a rotational position within the target rangeof the rotational position by performing the motor control process ofthe first embodiment.

Therefore, by adjusting the rotational position of the developing sidecoupling 430 of the new developing device 4 in advance, the damage inattaching the new developing device 4 caused by the collision of theprojection portions 170 and 440 of the drive side coupling 160 and thedeveloping side coupling 430 can be reduced.

Second Embodiment

In the following, the motor control process in a case where the motor130 has the brake function will be described.

In a case where the motor 130 has the brake function, the rotating motor130 can be stopped quicker by transmitting the brake signal from themotor control unit 112 to the motor driver 120 to have the brakefunction operate.

FIG. 9 is another diagram for illustrating an example relationshipbetween the variance of stop position of the drive side coupling 160 andthe rotational speed of the motor 130. In FIG. 9, a case where the motor130 has the brake function and a case where the motor 130 does not havethe brake function are shown.

As shown in FIG. 9, the variance of the stop position at the same speedis smaller in the case where the motor 130 has the brake function incomparison to the case where the motor 130 does not have the brakefunction. Therefore, a maximum rotational speed of the motor 130 forsuppressing the variance of the stop position to be within the range ofangle 30° can be set as rotational speed V2 that is greater than themaximum rotational speed V1 set in a case where the motor 130 does nothave the brake function.

Thus, in a case where the motor 130 has the brake function, time takenfor the motor control process can be reduced since the variance of thestop position can be suppressed even when the motor 130 is stopped whilerotating at a greater rotational speed which is less than the rotationalspeed in the normal drive.

FIG. 10 is a flowchart for illustrating an example motor control processof the second embodiment.

For example, in a case where the developing device 4 is detached fromthe image forming apparatus 1 to be replaced with new one, as shown inFIG. 10, in step S201, the motor speed setting unit 111 sets therotational speed of the motor 130. For example, the rotational speed ofthe motor 130 is set to be equal to or less than the rotational speed V2which is less than the rotational speed of the normal drive for formingan image by the image forming apparatus 1, etc., and where the varianceof the stop position of the drive side coupling 160 can be suppressed tobe within a predetermined range of the rotational position.

In step S202, the motor control unit 112 transmits the enable signal atthe low level to the motor driver 120 to have the motor 130 rotate atthe rotational speed set by the motor speed setting unit 111.

In step S203, the motor control unit 112 determines whether therotational speed of the motor 130 reaches the set rotational speed basedon the lock signal transmitted from the motor driver 120.

In a case where the rotational speed of the motor 130 is determined toreach the set rotational speed, the process is proceeded to step S204,and the rotational position acquiring unit 113 acquires the detectionresult of the rotational position detection sensor 150 and determineswhether the rotational position of the driving shaft 140 and the driveside coupling 160 reaches a predetermined rotational position.

Upon the rotational position detection sensor 150 detecting that thedrive side coupling 160 is at the predetermined rotational position, themotor control unit 112 transmits the brake signal to the motor driver120 to have the brake function of the motor 130 operate in step S205. Instep S206, the motor control unit 112 transmits the enable signal at thehigh level to the motor driver 120 to have the motor 130 stopped.

FIG. 11 is a diagram for illustrating the motor control in the secondembodiment.

The timing diagram shown in FIG. 11 illustrates the motor control indetaching the developing device. As shown in FIG. 11, for example, themotor control unit 112 outputs the clock signal at a frequency forhaving the motor 130 rotate at the rotational speed set by the motorspeed setting unit 111 to the motor driver 120. Also, the motor controlunit 112 transmits the enable signal at the low level to the motordriver 120, thereby having the motor 130 start to rotate.

Upon the rotational speed of the motor 130 reaching the set rotationalspeed, the lock signal at the high level is transmitted from the motordriver 120 to the motor control unit 112. Upon the rotational positionacquiring unit 113 receiving a detection signal from the rotationalposition detection sensor 150 during the motor 130 rotating at the setrotational speed, the motor control unit 112 transmits the brake signalto the motor driver 120 to have the brake function of the motor 130operate. Then, the motor control unit 112 transmits the enable signal atthe high level to the motor driver 120 to stop driving the motor 130.Here, the lock signal at the low level is transmitted from the motordriver 120 to the motor control unit 112 upon the rotational speed ofthe motor 130 being less than the set rotational speed.

Additionally, although in the example shown in FIG. 11, the motorcontrol process starts in a state where the motor 130 is stopped, themotor control process of the second embodiment may start while the motor130 is driven as described in the first embodiment.

Similarly to the first embodiment, according to the motor controlprocess of the second embodiment, the drive side coupling 160 is stoppedat a rotational position within the target range of the rotationalposition. Therefore, the damage in replacing the developing device 4caused by the collision of the projection portions 170 and 440 of thedrive side coupling 160 and the developing side coupling 430 can bereduced.

Also, in the second embodiment, the rotating motor 130 can be stoppedquicker by having the brake function of the motor 130 operate.Therefore, the motor control process can be completed in a short period.

Third Embodiment

In the following, for example, the motor control process in a case wherea developing device 4S for developing the white toner is replaced withanother developing device 4S for developing the transparent toner willbe described.

In a case where the developing device 4S is replace with that of anothercolor in the image forming apparatus 1, the toner bottle 21S will bereplaced. However, the toner of the color may be mixed with the toner ofthe other color if the toner of the color still remains in thesub-hopper 22 or a toner supply path between the sub-hopper 22 and thedeveloping device 4S.

Therefore, in the third embodiment, a process for eliminating theremained toner from the sub-hopper 22 or the toner supply path betweenthe sub-hopper 22 and the developing device 4S is performed before thedeveloping device 4S to be replaced with new one is detached.

FIG. 12 is a flowchart for illustrating an example motor control processof the third embodiment.

For example, in a case where the developing device 4S of a color isreplace with that of another color in the image forming apparatus 1, thetoner remained in the sub-hopper 22S is ejected to the developing device4S in step S301.

When the toner is ejected from the sub-hopper 22S to the developingdevice 4S, for example, the motor speed setting unit 111 sets therotational speed of the motor 130 to be Vr1 in step S302. In step S303,the motor control unit 112 transmits the enable signal at the low levelto the motor driver 120 to have the motor 130 rotate at the rotationalspeed Vr1 set by the motor speed setting unit 111.

In the developing device 4S, for example, the developer conveyance screwrotates, which is connected to the driven shaft 420 rotated by the motor130 through a transmission means, thereby ejecting the toner having beenejected from the sub-hopper 22S outside the developing device 4S throughthe toner outlet 411.

Here, in step S302, preferably, the motor speed setting unit 111 setsthe rotational speed Vr1 of the motor 130 to be great to the extentpossible so that the toner remained in the sub-hopper 22S is quicklyejected from the developing device 4S. When ejecting the toner from thesub-hopper 22S, for example, the rotational speed Vr1 is preferably setto be greater than the rotational speed V1 and V2 shown in FIG. 9 sincethe variance of the stop position of the drive side coupling 160 doesnot need to be considered.

In step S304, the toner residual amount acquiring unit 114 acquires thedetection result of the residual amount detection sensor 23S of thetoner supply unit 20S and determines whether the residual amount of thetoner in the sub-hopper 22S is less than a predetermined amount. Thetoner is continued to be sent from the sub-hopper 22S to the developingdevice 4S to be ejected from the toner outlet 411 until the residualamount of the toner in the sub-hopper 22S is determined to be less thanthe predetermined amount.

Upon the residual amount of the toner in the sub-hopper 22S beingdetermined to be less than the predetermined amount, the motor controlunit 112 transmits the brake signal to the motor driver 120 in stepS305, thereby having the brake function of the motor 130 operate. Instep S306, the motor control unit 112 transmits the enable signal at thehigh level to the motor driver 120 to stop driving the motor 130.

In step S307, for example, the motor speed setting unit 111 sets therotational speed of the motor 130 to be Vr2. In step S308, the motorcontrol unit 112 transmits the enable signal at the low level to themotor driver 120 to have the motor 130 rotate at the rotational speedVr2 set by the motor speed setting unit 111.

Here, in step S307, for example, the motor speed setting unit 111 setsthe rotational speed Vr2 to be less than the rotational speed in thenormal drive for forming an image by the image forming apparatus 1,etc., and equal to or less than the rotational speed V2 shown in FIG. 9so that the stop position of the drive side coupling 160 comes within atarget range of the rotational position.

In step S309, the motor control unit 112 determines whether therotational speed of the motor 130 reaches the set rotational speed basedon the lock signal transmitted from the motor driver 120.

In a case where the rotational speed of the motor 130 is determined toreach the set rotational speed, the process is proceeded to step S310,and the rotational position acquiring unit 113 acquires the detectionresult of the rotational position detection sensor 150 and determineswhether the rotational position of the driving shaft 140 and the driveside coupling 160 reaches a predetermined rotational position.

Upon the rotational position detection sensor 150 detecting that thedrive side coupling 160 is at the predetermined rotational position, themotor control unit 112 transmits the brake signal to the motor driver120 to have the brake function of the motor 130 operate in step S311. Instep S312, the motor control unit 112 transmits the enable signal at thehigh level to the motor driver 120 to have the motor 130 stopped.

Additionally, the motor 130 may not have the brake function. In thiscase, processes performed in step S305 and step S311 are omitted, andfor example, the rotational speed of the motor 130 set in step S307 isless than the rotational speed in the normal drive for forming an imageby the image forming apparatus 1, etc., and equal to or less than therotational speed V1 shown in FIG. 6 and FIG. 9.

Additionally, although in the example shown in FIG. 12, the motor 130 isstopped in steps S305 and S306, the motor control process of the thirdembodiment may start while the motor 130 is driven.

According to the motor control process of the third embodiment, thedifferent color toner mixing can be prevented since the toner remainedin the sub-hopper 22S is quickly ejected from the developing device 4Swhen the developing device 4S of the color is replace with a developingdevice 4S of another color. Also, similarly to the first embodiment andthe second embodiment, the drive side coupling 160 can be stopped at arotational position within a target range of the rotational position.Therefore, the damage in replacing the developing device 4S caused bythe collision of the projection portions 170 and 440 of the drive sidecoupling 160 and the developing side coupling 430 can be reduced.

The motor control processes described in the first embodiment and thesecond embodiment may be always performed when the developing device 4driven in the normal drive of the motor 130 is sopped, or they may beperformed when the operational unit 60 of the image forming apparatus 1accepts an instruction for setting the operation mode to be thereplacement mode of the developing device 4. Also, for example, themotor control processes described in the first embodiment and the secondembodiment are performed when the developing device 4 is stopped and theuser's instruction for setting the operation mode to be the replacementmode of the developing device 4 is accepted. For example, the motorcontrol processes described in the third embodiment is performed whenthe user's instruction for setting the operation mode to be thereplacement mode of the developing device 4S is accepted.

As described above, according to the driving apparatus 100 described inthe embodiments, the motor 130 is controlled so that the drive sidecoupling 160 is stopped at a certain rotational position when thedeveloping device 4, which is the driven apparatus, is replaced.

Therefore, by adjusting the rotational position of the developing sidecoupling 430 of the newly attached developing device 4 in advance, thedamages to the drive side coupling 160 and the developing side coupling430 caused by the collision of the projection portions 170 and 440 ofthe drive side coupling 160 and the developing side coupling 430 can bereduced. Hence, the durability of the coupling part for coupling thedriving apparatus and an apparatus driven by the driving apparatus canbe maintained, where the coupling part is the drive side coupling 160 ofthe driving apparatus 100 and the apparatus driven by the drivingapparatus is the developing device 4.

For example, in the image forming apparatus 1 described in theembodiments, the damages to the drive side coupling 160 and thedeveloping side coupling 430 can be reduced even if the developingdevice 4S is frequently replaced. Therefore, in the image formingapparatus 1, the developing device 4S can be repeatedly and smoothlyattached/detached, and for example, the driving-force of the motor 130of the driving apparatus 100 can be transmitted to the developing device4S without being reduced through the drive side coupling 160 or thedeveloping side coupling 430.

Additionally, in the embodiments described above, although the drivingapparatus 100 drives the developing device 4, the detachable units suchas a photoconductor drum 2, the intermediate transfer belt 8, thesecondary transfer roller 9, or the fixing device 50 may be driven witha similar configuration. Also, in the embodiments described above,although the driving apparatus 100 provided for the image formingapparatus 1 is described, the driving apparatus 100 may be provided foran apparatus other than the image forming apparatus 1 as long as itincludes a detachable unit.

Also, in the embodiments described above, although anelectrophotographic image forming apparatus for forming an image offull-color is described as the image forming apparatus 1, the imageforming apparatus 1 may not be the electrophotographic image formingapparatus and is not limited to the configuration described above aslong as it includes a detachable unit.

Further, the functions of the driving apparatus 100 described in theembodiments are achieved by executing a program by a computer, where therespective processes described above are encoded in a programminglanguage suitable for the driving apparatus 100 described in theembodiments to create the program. The program for achieving thefunctions of the driving apparatus 100 described in the embodiments maybe stored in a computer readable recording medium.

Herein above, although the invention has been described with respect toa specific embodiment for a complete and clear disclosure, the appendedclaims are not to be thus limited but are to be construed as embodyingall modifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth. The present application is based on Japanese Priority ApplicationNo. 2014-223088 filed on Oct. 31, 2014, and Japanese PriorityApplication No. 2015-194992 filed on Sep. 30, 2015, the entire contentsof which are hereby incorporated herein by reference.

What is claimed is:
 1. A driving apparatus comprising: a driving unitconfigured to rotate a driving shaft; a speed setting unit configured toset a rotational speed at which the driving unit rotates the drivingshaft; a driving shaft joint connected with the driving shaft to rotatewith the driving shaft for transmitting driving-force to a drivenapparatus, the driving shaft joint being fitted into a driven shaftjoint connected with the driven apparatus that is made detachable; arotational position detection unit configured to detect a predeterminedrotational position of the driving shaft joint; and a driving controlunit configured to control the driving unit; wherein upon an instructionindicating that the driven apparatus will be detached being given to thedriving control unit, the driving control unit controls the driving unitto stop the rotating driving shaft based on a detection result of therotational position detection unit after the speed setting unit sets therotational speed of the driving shaft to be a first rotational speed,the first rotational speed being less than a normal rotational speed ofthe driving shaft set in normal operation of the driven apparatus. 2.The driving apparatus as claimed in claim 1, wherein the driving unit isa DC motor.
 3. The driving apparatus as claimed in claim 2, wherein theDC motor has a brake function, and upon the instruction indicating thatthe driven apparatus will be detached being given, the driving controlunit has the brake function of the DC motor operate based on thedetection result of the rotational position detection unit.
 4. An imageforming apparatus including the driving apparatus as claimed in claim 1.5. The image forming apparatus as claimed in claim 4, comprising: atonner supply unit configured to supply toner to the driven apparatus;and a residual amount detection unit configured to detect a residualamount of the toner in the tonner supply unit; wherein the drivenapparatus includes a developing unit configured to develop an image byusing the toner and a toner outlet for ejecting redundant toner, andupon the instruction indicating that the driven apparatus will bedetached being given, the speed setting unit sets the rotational speedof the driving shaft to be a second rotational speed until the residualamount of the toner detected by the residual amount detection unitbecomes equal to or less than a predetermined amount, the secondrotational speed being greater than the first rotational speed.
 6. Amethod of driving control for a driving apparatus including a drivingunit configured to rotate a driving shaft, a driving shaft jointconnected with the driving shaft to rotate with the driving shaft fortransmitting driving-force to a driven apparatus, the driving shaftjoint being fitted into a driven shaft joint connected with the drivenapparatus that is made detachable, the method comprising the steps of:setting a rotational speed at which the driving unit rotates the drivingshaft to be a first rotational speed, the first rotational speed beingless than a normal rotational speed of the driving shaft set in normaloperation of the driven apparatus; detecting a predetermined rotationalposition of the driving shaft joint; and upon an instruction indicatingthat the driven apparatus will be detached being given, controlling thedriving unit to stop the rotating driving shaft based on a detectionresult of the step of detecting.
 7. A non-transitory computer-readablerecording medium having stored therein a program for causing a computerto perform the method as claimed in claim 6.